User apparatus, base station apparatus, and method in mobile communication system

ABSTRACT

A user apparatus transmits an uplink control signal to a base station apparatus using a single carrier scheme. The user apparatus includes: a unit configured to receive a downlink control signal and a downlink data signal; a unit configured to prepare acknowledgement information indicating positive acknowledgement or negative acknowledgement for the downlink data signal; a unit configured to prepare the uplink control signal including the acknowledgement information; a unit configured to transmit the uplink control signal using different resources which are different from resources that can be used for an uplink data signal; and a storage unit configured to store predetermined correspondence relationship which uniquely associates resources of the downlink control signal or the downlink data signal with resources used for the uplink control signal.

TECHNICAL FIELD

The present invention relates to the next generation mobilecommunication scheme. More particularly, the present invention relatesto a user apparatus, a base station apparatus, and a method in themobile communication system of the next generation mobile communicationscheme.

BACKGROUND ART

In this kind of technical field, research and development on the nextgeneration communication system is rapidly progressing. In thecommunication system considered as of now, from the view point ofwidening coverage while reducing PAPR (Peak-to-Average Power Ratio), itis proposed to use a single carrier scheme for uplink. In addition, inthis communication system, for both of uplink and downlink, radioresources are properly assigned, as a form of a shared channel which isshared by a plurality of users, according to communication states ofeach user and the like. More particularly, a data signal of a user inthe uplink is transmitted by a physical uplink shared channel (PUSCH).The terms “channel” and “signal” may be used synonymously as long asthere is no fear of confusion. A data signal of a user in the downlinkis transmitted by a physical downlink shared channel (PDSCH).

Processing for determining assignment is called scheduling. In order toproperly perform scheduling in the uplink, each user apparatus transmitsa reference signal (also called as a pilot channel) to a base station,and the base station evaluates the channel state of the uplink based onthe reception quality. In addition, in order to perform scheduling inthe downlink, the base station transmits a reference signal to the userapparatus, and the user apparatus reports to the base stationinformation indicating channel state (CQI: Channel Quality Indicator)based on the reception quality of the reference signal. Based on the CQIreported from each user apparatus, the base station evaluates thechannel state of the downlink to perform scheduling of downlink. Thecontents of scheduling are transmitted to each user apparatus by adownlink control signal. This control signal is called a downlink L1/L2control channel or a downlink L1/L2 control signal.

As uplink control signals, there are control information (called firstcontrol information, for the sake of convenience) that should betransmitted by accompanying an uplink data signal, and controlinformation (called second control information, for the sake ofconvenience) that is transmitted irrespective of the presence or absenceof the uplink data signal. The first control information includesinformation necessary for demodulation of a data signal, such asmodulation scheme, channel coding rate and the like of the data signal.The second control information includes CQI information of downlinkchannel, acknowledgement information (ACK/NACK) of downlink data signal,and information of resource assignment request, and the like. Therefore,there is a possibility that the user apparatus transmits only the firstcontrol information, only the second control information, or both of thefirst and the second control information by using the uplink controlsignal.

When a resource block (radio resource) is assigned for transmitting anuplink data channel, the first control information (and second controlinformation as necessary) is transmitted by the resource block. On theother hand, when the uplink data signal is not transmitted, it isconsidered to transmit the second control signal by using dedicatedresources (dedicated band). In the following, an outline of an exampleis described in which a band is used in such a way.

FIG. 1 shows a band use example of uplink. FIG. 1 shows resources (aplurality of resource blocks) for transmitting the physical uplinkshared channel (PUSCH) that is the uplink data signal, and showsresources (corresponding to the dedicated band) for a user to which theresources for the PUSCH are not assigned to transmit the uplink controlsignal. The latter is called a physical uplink control channel (PUCCH).In the example shown in the figure, one or more of four resource blocksare assigned to users, and a first hopping control signal and a secondhopping control signal are prepared in a transmission time interval(TTI), and a third hopping control signal and a fourth hopping controlsignal are prepared in the following TTI. Each hopping control signalcorresponds to PUCCH. By performing hopping with respect to time andfrequency in TTIs or subframes, diversity effect can be obtained. Eachof the first to fourth hopping control signals may be occupied by oneuser or may be multiplexed by a plurality of users. This type oftransmission scheme of the uplink control signals is described in thenon-patent document 1.

-   -   [Non-patent document 1] 3GPP, R1-071245

DISCLOSURE OF THE INVENTION Problem to be Solved by the Invention

In the above-mentioned proposed methods, it is necessary to report, tothe user apparatus, which resource should be used for the uplink controlsignal by using the downlink L1/L2 control signal. As to the uplinkcontrol signal for a user to which resources are not assigned fortransmission of the uplink data signal, it is necessary to report, toeach user apparatus, which slot in the dedicated resources should beused for transmission of the uplink control signal. The uplink controlsignal may only include acknowledgment information (ACK/NACK), forexample. Essentially, only one bit is necessary for the acknowledgmentinformation. But, the acknowledgment information plays a central role inretransmission control, and, true or false of the acknowledgmentinformation largely affects throughput of data transmission. However, inthe conventional method, for transmitting the acknowledgmentinformation, which is merely one bit, using the uplink, it is necessaryto report, to the user apparatus, which resource should be used fortransmission of the acknowledgment information by using the downlinkL1/L2 control signal each time. Thus, there is a problem that suchprocessing is inefficient. In addition, there is a problem in that it isdifficult to enhance quality of the acknowledgment information since itis hard to obtain coding gain for the acknowledgment information havingmerely one bit.

An object of the present invention is to efficiently report, to the userapparatus, which resource should be used for transmitting, in theuplink, control information that has a small number of bits, but thatrequires high quality.

Means for Solving the Problem

In the present invention, a user apparatus which transmits an uplinkcontrol signal to a base station apparatus using a single carrier schemeis used. The user apparatus includes: a unit configured to receive adownlink control signal and a downlink data signal; a unit configured toprepare acknowledgement information indicating positive acknowledgementor negative acknowledgement for the downlink data signal; a unitconfigured to prepare the uplink control signal including theacknowledgement information; a unit configured to transmit the uplinkcontrol signal using different resources which are different fromresources that can be used for an uplink data signal; and a storage unitconfigured to store predetermined correspondence relationship whichuniquely associates resources of the downlink control signal or thedownlink data signal with resources used for the uplink control signal.

Effect of the Present Invention

According to the present invention, it becomes possible to efficientlyreport, to the user apparatus, information indicating which resourceshould be used in uplink for transmitting control information that has asmall number of bits, but that requires high quality.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing a band use example used in a mobilecommunication system;

FIG. 2 shows a block diagram of a user apparatus according to a firstembodiment of the present invention;

FIG. 3 is a diagram showing examples of TTI, subframe and block;

FIG. 4 is a diagram for explaining properties of CAZAC code;

FIG. 5 is a diagram showing a situation in which each long block LB ismultiplied by a factor (modulating data);

FIG. 6 is a diagram showing a situation in which each long block LB ismultiplied by factors (modulating data and block spread code);

FIG. 7 shows a block diagram of a base station apparatus according to afirst embodiment of the present invention;

FIG. 8 is a flowchart showing an operation example of the presentinvention;

FIG. 9 is a flowchart for specifying code information from broadcastinformation and assigned number;

FIG. 10 is a diagram showing setting examples of CAZAC codes, cyclicshift amounts and bands realized by executing the flow shown in FIG. 9;

FIG. 11 is a diagram showing an example of correspondence relationshipbetween resources of downlink control signal addressed to the userapparatus and resources of the uplink control signal;

FIG. 12 is a diagram showing a situation in which specific resources arereserved for a user performing persistent scheduling;

FIG. 13 shows a block diagram of the user apparatus according to asecond embodiment of the present invention;

FIG. 14 shows a block diagram of the base station apparatus according tothe second embodiment of the present invention; and

FIG. 15 is a diagram showing an example of correspondence relationshipbetween resource blocks addressed to the user apparatus and resources ofthe uplink control signal.

DESCRIPTION OF REFERENCE SIGNS

-   304 ACK/NACK determination unit-   306 block-by-block modulation pattern generation-   308 block-by-block modulation unit-   310 discrete Fourier transform unit (DFT)-   312 subcarrier mapping-   314 inverse fast Fourier transform unit-   316 cyclic prefix (cp) adding unit-   318 multiplexing unit-   320 RF transmission circuit-   322 power amplifier-   324 duplexer-   331 CAZAC sequence number setting unit-   332 CAZAC code generation unit-   333 cyclic shift number setting unit-   334 cyclic shift unit-   335 block spread code setting unit-   336 block spreading unit-   337 frequency setting unit-   338 reference signal generation unit-   340, 340′ determination unit-   342, 342′ code information and resource information unit-   702 duplexer-   704 RF reception circuit-   706 reception timing estimation unit-   708 fast Fourier transform unit (FFT)-   710 channel estimation unit-   712 subcarrier demapping unit-   714 frequency domain equalizing unit-   716 inverse discrete Fourier transform unit (IDFT)-   718 demodulation unit-   722 scheduler-   742, 742′ code information and resource information unit

PREFERRED EMBODIMENTS FOR CARRYING OUT THE INVENTION

For the sake of convenience of explanation, although the presentinvention is described by being classified into some embodiments,classification into each embodiment is not essential in the presentinvention, and equal to or more than two embodiments may be used asnecessary. Although specific numerical values are in explanation, suchnumerical values are merely examples, so that any appropriate value maybe used unless specified otherwise.

Embodiment 1

FIG. 2 shows a block diagram of a user apparatus according to anembodiment of the present invention. FIG. 2 shows an ACK/NACKdetermination unit 304, a block-by-block modulation pattern generationunit 306, a block-by-block modulation unit 308, a discrete Fouriertransform (DFT) unit 310, a subcarrier mapping unit 312, an inverse fastFourier transform unit (IFFT) 314, a cyclic prefix (CP) adding unit 31,a multiplexing unit 318, a RF transmission circuit 320, a poweramplifier 322, a duplexer 324, a CAZAC sequence number setting unit 331,a CAZAC code generation unit 332, a cyclic shift number setting unit333, a cyclic shift unit 334, a block spread code setting unit 335, ablock spreading unit 336, a frequency setting unit 337, a referencesignal generation unit 338, a determination unit 340 for L1/L2 controlinformation number and the number of times of retransmission, and a codeinformation and resource information unit 342.

The ACK/NACK determination unit 304 determines whether there is an errorin each of packets that form the received downlink data signal, andoutputs a determination result as acknowledgement information. Theacknowledgement information may be represented as positiveacknowledgement (ACK) indicating there is no error or negativeacknowledgement (NACK) indicating there is an error. Since it is onlynecessary that the acknowledgement information can represent presence orabsence of an error in the received packet, the acknowledgementinformation can be represented essentially by one bit. But, theacknowledgement information may be represented by a larger number ofbits.

The block-by-block modulation pattern generation unit 306 shapes each ofchannel state information (CQI) and acknowledgment information(ACK/NACK) into a block-by-block modulation pattern. A predeterminednumber of blocks are included in a subframe, and the subframe forms atransmission time interval (TTI) which is an assignment unit ofresources.

FIG. 3 shows examples of the subframe and the TTI. In the examples shownin the figure, TTI of 1.0 ms includes two subframes each being 0.5 ms,and each subframe includes six long blocks (LB) and two short blocks(SB). The long block is 66.7 μs, for example. The short block is 33.3μs, for example. The numerical values are merely examples, and can bechanges as necessary. Generally, the long block is used for transmittingdata (control signal, data signal and the like) which is unknown for thereceiving side, and the short block is used for transmitting data (pilotchannel and the like) which is known to the receiving side. In theexample shown in the figure, one TTI includes 12 long blocks (LB1-LB12)and 4 short blocks (SB1-SB4).

The block-by-block modulation pattern generation unit 306 shown in FIG.2 determines correspondence relationship between one or more of the 12blocks (LB1-LB12) and bits representing channel state information (CQI),and determines correspondence relationship between one or more of the 12blocks (LB1-LB12) and bits representing acknowledgement information(ACK/NACK). The user apparatus transmits only channel state information,transmits only acknowledgement information, or transmits both of them,by using an uplink control signal. Therefore, (A) all of the 12 blocksmay be associated with channel state information, (B) all of the 12blocks may be associated with acknowledgement information, or (C) a partof 12 blocks may be associated with the channel state information andthe remaining part may be associated with the acknowledgementinformation. In any way, based on the correspondence relationship, onefactor is prepared for each of the 12 blocks, so that 12 factors (firstfactor-twelfth factor) are prepared in total per one TTI.

The block-by-block modulation unit 308 forms a first long block bymultiplying, by the first factor, all chips of a CAZAC code sequence(the length of the sequence can be associated with one long block)assigned to the user apparatus, and forms a second long block bymultiplying all chips of the same CAZAC code sequence by the secondfactor, and after that, similarly, the block-by-block modulation unit308 forms a twelfth long block by multiplying all chips of the sameCAZAC code sequence by the twelfth factor, so that the block-by-blockmodulation unit 308 derives an information sequence to be transmitted inone TTI. The CAZAC code sequence used commonly for all blocks is anorthogonal code sequence assigned in the residing cell for identifyingthe user apparatus. Properties of the CAZAC code sequence are describedlater.

The discrete Fourier transform unit (DFT) 310 performs discrete Fouriertransform to transfer time series information into information of thefrequency domain.

The subcarrier mapping unit 312 performs mapping in the frequencydomain. Especially when the frequency division multiple access (FDM)scheme is used for multiplexing a plurality of user apparatuses, thesubcarrier mapping unit 312 performs mapping of signals based on bandsset in the frequency setting unit 336. There are two types of FDMschemes which are a localized FDM scheme and a distributed FDM scheme.In the localized FDM scheme, a continuous band is assigned for eachindividual user on the frequency axis. In the distributed FDM scheme, adownlink signal is generated such that the signal includes discontinuousfrequency components over a wide band (over the whole of the specificband F_(RB2) for uplink control signal).

The inverse fast Fourier transform unit (IFFT) 314 restores the signalof the frequency domain into a signal of the time domain by performinginverse Fourier transform.

The cyclic prefix (CP) adding unit 316 adds a cyclic prefix toinformation to be transmitted. The cyclic prefix (CP) functions as aguard interval for absorbing multipath propagation delay and forabsorbing differences of reception timing among a plurality of users inthe base station.

The multiplexing unit 318 multiplexes the reference signal intoinformation to be transmitted so as to generate a transmission symbol.The reference signal is transmitted by the short block (SB1, SB2) shownin the frame configuration of FIG. 3. The reference signal is a signalthat includes a pattern which is known to the transmission side and thereception side, and can be also referred to as a pilot signal, a pilotchannel, a training signal, and the like.

The RF transmission circuit 320 performs processing such asdigital-analog conversion, frequency conversion, band limitation and thelike for transmitting the transmission symbol by a radio frequency.

The power amplifier 332 adjusts transmission power.

The duplexer 324 properly separates a transmission signal and a receivedsignal such that simultaneous communication is realized.

The CAZAC sequence number setting unit 331 sets a sequence number ofCAZAC code sequence used by the user apparatus. The CAZAC code will bedescribed later with reference to FIG. 4.

The CAZAC code generation unit 332 generates the CAZAC code sequenceaccording to the set sequence number.

The cyclic shift number setting unit 333 sets a cyclic shift amount ofthe CAZAC code sequence to be used by the user apparatus according tocode information.

The cyclic shift unit 334 derives another code by cyclically rearrangingthe CAZAC code sequence according to the set cyclic shift amount.

In the following, an outline of the CAZAC code is described.

As shown in FIG. 4, it is assumed that a code length of a CAZAC code Ais L. For the sake of convenience of explanation, although it is assumedthat the code length corresponds to a time duration of L samples or Lchips, such assumption is not essential for the present invention.Another code B is generated by moving a series of Δ samples (shaded areain the figure) including the last sample (L-th sample) of the CAZAC codeA to the top of the CAZAC code A as shown in the lower side of FIG. 4.In this case, the CAZAC codes A and B are orthogonal to each other withrespect to Δ=0˜(L−1). That is, a CAZAC code is orthogonal to a codeobtained by cyclically shifting the CAZAC code. Therefore, when onesequence of a CAZAC code of the code length L is prepared, L codes whichare orthogonal to each other can be prepared theoretically. A CAZAC codeA is not orthogonal to another CAZAC code C that cannot be obtained bycyclically shifting the CAZAC code A. However, a cross-correlation valuebetween the CAZAC code A and a random code which is not a CAZAC code isremarkably greater than a cross-correlation value between the CAZAC codeA and the CAZAC code C. Thus, CAZAC code is preferable also from theviewpoint of reducing cross-correlation amount (interference amount)between non-orthogonal codes.

In the present embodiment, each user apparatus uses a CAZAC codeselected from among a group of CAZAC codes having such properties (acode sequence group derived by cyclically shifting a CAZAC code). In thepresent embodiment, among L codes that are orthogonal to each other,L/L_(Δ) codes obtained by cyclically shifting a basic CAZAC code byΔ=n×L_(Δ) are actually used as reference signals by mobile stations(n=0, 1, . . . , (L−1)/L_(Δ)). L_(Δ) is an amount determined based on amultipath propagation delay amount. In doing this way, orthogonalrelationship can be maintained in uplink control signals transmittedfrom individual user apparatuses under a multipath propagationenvironment. Details of the CAZAC code are described in D. C. Chu,“Polyphase codes with good periodic correlation properties”, IEEETrans.Inform.Theory, vol. IT-18, pp. 531-532, July 1972; 3GPP,R1-050822, Texas Instruments, “On allocation of uplink sub-channels inEUTRA SC-FDMA”, for example.

The block spreading unit 336 shown in FIG. 2 prepares a set ofpredetermined number of factors (block spread codes) and multiplies eachof long blocks (LB) by each factor. The block spread code is anorthogonal code sequence, and which orthogonal code sequence is used isspecified by information from a code information specifying unit 330.

FIG. 5 shows subframes of a first user apparatus UE1 and a second userapparatus UE2 in which multiplication by the block spread code is notperformed. Both of the first and the second user apparatuses use a CAZACcode sequence (CAZAC1). But, the second user apparatus uses a cyclicshift amount Δ which is different from that used by the first userapparatus. Therefore, two subframes transmitted by the user apparatusesare orthogonal to each other. “Mod.a” indicates data to modulate a firstlong block for the first user apparatus UE1, that is, “Mod.a” indicatesa factor used for multiplication. “Mod.a”-“Mod.f” correspond to firstfactor to sixth factors (or seventh to eighth factors) for the firstuser apparatus UE1. “Mod.u”-“Mod.z” correspond to first factor to sixthfactors (or seventh to eighth factors) for the second user apparatusUE1. Each factor (modulating data) may include any information.

FIG. 6 shows a situation in which long blocks of each of the first andthe second user apparatuses UE1 and UE2 are multiplied by block spreadcodes. In the example shown in the figure, a factor (separately frommodulating data) is prepared every two long blocks. This factor forms ablock spread code (BLSC). As shown in the broken line frame, anorthogonal code (1, 1) is prepared for the first user apparatus UE1, andan orthogonal code (1, −1) is prepared for the second user apparatusUE2. As described in the first embodiment, as long as one or moreresource blocks are multiplied by a same factor (value), orthogonalityof the CAZAC code that forms the long block is not lost.

Therefore, as shown in the figure, when a set of factors by which theblocks is multiplied is codes that are orthogonal among users, users canbe made orthogonal to each other using the codes while maintainingorthogonality of the CAZAC code. However, the blocks which aremultiplied by an orthogonal code should have the same contents. In theexample shown in the figure, for the first user UE1, each of the firstfactor and the second factor is “Mod.a”, each of the third factor andthe fourth factor is “Mod.b”, and each of the fifth factor and the sixthfactor is “Mod.c”. Similarly, for the second user UE2, each of the firstfactor and the second factor is “Mod.x”, each of the third factor andthe fourth factor is “Mod.y”, and each of the fifth factor and the sixthfactor is “Mod.z”. Thus, contents of information carried by the first totwelfth factors are limited to some extent. But, the limitation is notcritical since the number of bits necessary for representing ACK/NACKetc. is relatively small.

Since the first and the second user apparatuses UE1 and UE2 can beidentified by the block spread codes (1, 1) and (1, −1), the CAZAC codeshift amount used for the first and the second user apparatuses may bethe same (it is not essential to use different cyclic shift amounts Δ).For the sake of convenience of explanation, although factors by whichlong blocks are multiplied are described, the short blocks SB may bemultiplied by factors.

In the case when the frequency division multiplexing (FDM) scheme isapplied for an uplink control signal from a plurality of userapparatuses, the frequency setting unit 337 shown in FIG. 2 specifieswhich frequency should be used by each user apparatus.

The reference signal generation unit 338 prepares a reference signal tobe included in the uplink control signal. As mentioned above, thereference signal is transmitted using the short block (SB1,SB2) in theframe configuration shown in FIG. 3. The reference signal is also formedby a CAZAC code assigned to each user apparatus. The CAZAC code for thereference signal may be also specified by a sequence number and a cyclicshift amount.

Generally, the long block (LB) and the short block (SB) are different inlength, in time duration, or in number of chips, a CAZAC code C_(L)included in the long block (LB) and a CAZAC code C_(S) included in theshort block (SB) may be prepared separately. However, since both of themare used for a same user apparatus, there may be a relationship betweenthe CAZAC codes C_(L) and C_(S) (for example, a part of C_(L) may formC_(S)).

The unit 340 for determining the L1/L2 control information number anddetermining a number of times of retransmission demodulates and decodesthe downlink L1/L2 control signal to specify where control informationaddressed to the user apparatus is mapped. In other words, thedetermination unit 340 specifies a position number to which the controlinformation addressed to the user apparatus is mapped from amongmultiple pieces of control information of one or more users multiplexedin the downlink L1/L2 control information. For the sale of convenienceof explanation, it is assumed that control information of N users aremultiplexed into the downlink L1/L2 control signal, and that controlinformation to the particular user apparatus is mapped to a X-thposition. The determination unit 340 specifies information indicating“X”. In addition, when the signal received by the user apparatus is aretransmission packet, the determination unit 340 also specifies howmany times retransmission has been performed.

The code information and resource information unit 342 specifies codeinformation which includes information of a CAZAC code sequence(sequence number), a cyclic shift amount of CAZAC code sequence, atransmission band and the like, used by the user apparatus. The codeinformation may be derived based on broadcast information of thebroadcast channel, or may be reported from the base stationindividually. The individual reporting may be performed using signalingof the upper layer such as a L3 control signal. The code informationfurther specifies an orthogonal code sequence represented by a set offactors (block spread code sequence) by which each set of a pluralityblocks is multiplied.

The code information and resource information unit 342 refers to a listindicating correspondence relationship between “X” which is the downlinkL1/L2 control information number (number of times of retransmission, asnecessary) and resources of the uplink control signal in order tospecify resources by which the uplink control signal includingacknowledgement information should be transmitted.

FIG. 7 shows a base station apparatus according to an embodiment of thepresent invention. FIG. 7 shows a duplexer 702, an RF reception circuit704, a reception timing estimation unit 706, a fast Fourier transformunit (FFT) 708, a channel estimation unit 710, a subcarrier demappingunit 712, a frequency domain equalizing unit 714, an inverse discreteFourier transform unit (IDFT) 716, a demodulation unit 718, a scheduler722, and a code information and resource information unit 742.

The duplexer 702 properly separates between a transmission signal and areceived signal such that simultaneous communication is realized.

The RF reception circuit 704 performs processing such as digital analogconversion, frequency conversion, band limitation and the like forprocessing the received symbol in baseband.

The reception timing estimation unit 706 specifies reception timingbased on a synchronization channel or a reference signal in a receivedsignal.

The fast Fourier transform unit (FFT) 708 performs Fourier transform toconvert time series information to information in the frequency domain.

The channel estimation unit 710 estimates a channel state in the uplinkbased on reception state of the uplink reference signal, and outputsinformation for performing channel compensation.

The subcarrier demapping unit 712 performs demapping in the frequencydomain. This processing is performed in response to mapping in thefrequency domain performed in the individual user apparatuses.

The frequency domain equalizing unit 714 performs equalization of thereceived signal based on the channel estimation value.

The inverse discrete Fourier transform unit (IDFT) 716 restores afrequency domain signal into a time domain signal by performing inversediscrete Fourier transform.

The demodulation unit 718 demodulates the received signal. As to thepresent invention, an uplink control signal is demodulated, so that thedemodulation unit 718 outputs channel state information (CQI) ofdownlink channel and/or acknowledgement information (ACK/NACK) fordownlink data signal.

The scheduler 722 determines assignment in the downlink based on qualityof the channel state information (CQI) of the downlink channel and othercriteria. In addition, the scheduler 722 determines uplink resourceassignment based on reception result of the reference signal transmittedfrom each user apparatus and other criteria. The determined informationis output as scheduling information. The scheduling informationspecifies frequency, time, transmission format (data modulation schemeand channel coding rate) and the like used for transmitting signals.

In addition, the scheduler 722 reports, to the code information andresource information unit 742, information indicating where the controlinformation for each user apparatus is mapped in the downlink L1/L2control signal. The information indicates a position number to whichcontrol information of each user is mapped from among multiple pieces ofcontrol information of one or more users multiplexed in the downlinkL1/L2 control signal. In the above-mentioned example, controlinformation addressed to a user apparatus is mapped to an X-th position,and information of “X” is reported to the code information and resourceinformation unit 742 for the user apparatus.

Based on the assignment result by the scheduler, the code informationand resource information unit 742 specifies code information whichincludes a sequence number indicating a CAZAC code used by a userapparatus in the uplink, cyclic shift amount, usable frequency band,block spread code and the like. The code information may be commonlyreported to each user using the broadcast channel, or may be reportedindividually to individual users. In the former case, it is necessarythat each user apparatus uniquely derives specific code information forthe user apparatus from broadcast information.

Like the code information and resource information unit 342 (FIG. 2),the code information and resource information unit 742 refers to a listindicating correspondence relationship between X which is a downlinkL1/L2 control information number (number of times of retransmission asnecessary) and resources of the uplink control signal, and specifiesresources to be used for transmitting the uplink control signalincluding the acknowledgement information in the future.

FIG. 8 shows an operation procedure according to an embodiment of thepresent invention. In this operation example, general code informationrelated to all user apparatuses are transmitted by the broadcast channel(BCH). Each user apparatus uniquely derives code information specific tothe own apparatus from the broadcast information. The general codeinformation may include information indicating that there are N CAZACcode sequences (C#1, C#2, C#N) used in the cell, there are M cyclicshift amounts (0, L_(Δ), . . . , (M−1)×L_(Δ)) for each sequence, andthat frequency division multiplexing (FDM) scheme is used and there areF available bandwidths (Bw1, Bw2, BwF), and the like. As necessary, thecode information may include information on block spread code.

In step B1, the base station apparatus performs downlink scheduling, andthe base station apparatus sends a downlink control signal (L1/L2control signal), a downlink data signal and a reference signal to theuser apparatus.

In step M1, the user apparatus specifies information (code informationfor the user apparatus) related to the code used for an uplink controlsignal based on information included in the downlink control signal.

FIG. 9 shows an example of a method for specifying code information thatmay be used in step M1. For the sake of simplicity, it is assumed thattwo CAZAC code sequences (C#1, C#2) are prepared, three cyclic shiftamounts (0, L_(Δ), 2L_(Δ)) are prepared for each sequence, and that twoavailable bands (Bw1, Bw2) are prepared. Therefore, 2×3×2=12 userapparatuses can be identified. The numbers are merely examples, andother proper numbers may be used.

In step S1, the user apparatus recognizes an assigned number P(=1, 2, .. . , 12) of the user apparatus specified in the downlink L1/L2 controlsignal.

In step S2, the user apparatus determines whether the assigned number pis greater than 3 or not. When the determination result is No (when p=1,2 or 3), the sequence number is specified as C#1, the shift amount isspecified as (P−1)×L_(Δ), and the band is specified as Bw1. When theassigned number is greater than 3, the process flow goes to step S3.

In step S3, the user apparatus determines whether the assigned number pis greater than 6 or not. When the determination result is No (when p=4,5 or 6), the sequence number is specified as C#1, the shift amount isspecified as (P−1)×L_(Δ), and the band is specified as Bw2. When theassigned number is greater than 6, the process flow goes to step S4.

In step S4, the user apparatus determines whether the assigned number pis greater than 9 or not. When the determination result is No (when p=7,8 or 9), the sequence number is specified as C#2, the shift amount isspecified as (P−7)×L_(Δ), and the band is specified as Bw1. When theassigned number is greater than 9 (when p=10, 11 or 12), the sequencenumber is specified as C#2, the shift amount is specified as(P−10)×L_(Δ), and the band is specified as Bw2.

FIG. 10 shows examples of CAZAC codes, cyclic shift amounts and bandsrealized by executing the flow shown in FIG. 9. As shown in the figure,users are multiplexed using a code division multiplexing (CDM) schemeusing a CAZAC code of a same sequence, first. As the number of usersincreases, users are code-multiplexed using the same CAZAC code sequencein another band. After that, CDM is performed in each available band. Inother words, although CDM and FDM are performed, CDM is givenpreference. In the case when multiplexing users the number of which isgreater than the number of users that can be identified by code divisionmultiplexing using a CAZAC code sequence and using frequency divisionmultiplexing, another CAZAC code sequence is prepared, and users aremultiplexed by CDM, and CDM and FDM.

Assuming that N CAZAC code sequences (C#1, C#2, C#N) are prepared, Mcyclic shift amounts (0, L_(Δ), . . . , (M−1)×L_(Δ)) are prepared,frequency division multiplexing scheme (FDM) is used, and that Favailable bands (Bw1, Bw2, BwF) are prepared, the sequence number ofCAZAC code is represented as a value of (P/(M×F)) in which a fractionalportion is round up, a ((P−(n−1)×(M×F))/M)-th band is used, and thecyclic shift amount is represented as (P−((n−1)×(M×F))−(f−1)×M=Pmod M)times L_(Δ).

In the example described with reference to FIGS. 9 and 10, the userapparatus starts to use another band Bw2 at the time when the assignednumber or the number of multiplexed users exceeds three. However, evenwhen the number of multiplexed users is greater than 3 and equal to orless than 6, it can be considered to use the same band Bw1, and instead,use another CAZAC code sequence C#2. The CAZAC codes C#1 and C#2 are notorthogonal to each other in which one cannot be derived from another bycyclically shifting. However, the reason to use C#1 and C#2 is that thecross-correlation value is relatively small.

As mentioned above, code information of each user apparatus can bespecified from the broadcast information and the assignment informationp. The specified code information is provided to the CAZAC sequencenumber setting unit 331, the cyclic shift number setting unit 333, theblock spread code setting unit 335, the frequency setting unit 337 andthe reference signal setting unit 38 shown in FIG. 2, so that variousparameters are set.

In step M2 in FIG. 8, the user apparatus determines presence or absenceof an error for each packet of the downlink data signal. For example,the error detection may be performed using the cyclic redundancy check(CRC) method, or any other proper error detection method known in thistechnical field may be used. The user apparatus determines positiveacknowledgement ACK which indicates there is no error (or within apermissible range even if there is an error) or negative acknowledgementNACK which indicates there is an error, for each packet. The ACK and theNACK form the acknowledgment information.

In step M3, the user apparatus measures reception quality of thedownlink reference signal, and converts the measurement value to anumerical value within a range to derive the channel state information(CQI). For example, in the case when the reception quality (SIR and thelike) is represented as 32 levels, the user apparatus converts themeasurement result to a numerical value indicating what level thecurrent reception quality is, so that CQI that can be represented by 5bits is derived.

It is not essential that the steps M2 and M3 are performed in thisorder. The determination of the acknowledgement information and themeasurement of the channel state information may be performed at anyproper time.

In step M4, the user apparatus generates an uplink control signal forreporting, to the base station, both or one of the acknowledgementinformation (ACK/NACK) or the channel state information (CQI). Asmentioned above, the block-by-block modulation pattern generation unitshown in FIG. 2 prepares one factor for each of 12 blocks, so that 12factors (first factor-twelfth factor) are prepared for one TTI. One ormore of the 12 factors may represent the acknowledgement information,the channel state information or other information. The uplink controlsignal has a frame structure shown in FIGS. 3 and 6.

For example, the first long block (LB1) is generated by multiplying thewhole CAZAC code sequence (cyclically shifted) by the first factor. Thesecond long block (LB2) is generated by multiplying the same CAZAC codesequence by the second factor. After that, in the same way, a K-th longblock (LBK) is generated by multiplying the same CAZAC code by the K-thfactor. Accordingly, a frame for the uplink control signal including 12long blocks is generated. More properly, the frame includes a referencesignal formed by a CAZAC code.

The uplink control signal generated in this way is transmitted from theuser apparatus to the base station using a dedicated band. The userapparatus can uniquely determine which part in the dedicated band isused based on resource information. The resource information indicatespredetermined correspondence relationship between a mapping position inthe downlink L1/L2 control signal and resources of the uplink controlsignal, and is specified by the code information and resourceinformation units 342 and 742 shown in FIGS. 2 and 7.

For example, assuming that control information for a user apparatus ismapped to a X-th position in the downlink L1/L2 control signal whichincludes information of N users, the corresponding relationship uniquelyassociates X with slot (FIG. 1), CAZAC code (sequence number, cyclicshift amount), block spread code, frequency band and the like used forthe uplink control signal. This correspondence relationship is known tothe user apparatus and the base station apparatus. Accordingly,resources to be used for the uplink control signal includingacknowledgement information are uniquely derived based on informationindicating that “control information (control information accompanyingthe downlink data signal) addressed to the user apparatus is mapped tothe X-th position”, and the uplink control signal is transmitted usingthe resources.

FIG. 11 schematically shows such a predetermined correspondencerelationship. In the example shown in the figure, when controlinformation accompanying the downlink data signal addressed to a userapparatus (that is, control information including schedulinginformation) is mapped to an X-th position, ACK/NACK for the downlinkdata signal is transmitted by the first hopping control signal (FIG. 1).The downlink data signal may be a retransmission packet instead of a newpacket. In the case when a resource block used for the retransmissionpacket is specifically determined, the correspondence relationship isdetermined considering such information.

FIG. 12 shows a situation in which resources for the uplink controlsignal are reserved for a user performing persistent scheduling. Whendownlink communication based on persistent scheduling is performed, thedownlink L1/L2 control signal is not transmitted. In this case, anuplink control signal including ACK/NACK is transmitted by resourcesspecifically prepared as shown in FIG. 12.

In step B2 in FIG. 8, the base station apparatus receives uplink controlsignals from a plurality of user apparatuses, and demodulates thesignals. Each user apparatus transmits a similar uplink control signal.But, the uplink control signals use the same CAZAC code sequence havingdifferent cyclic shift amounts, different bands, CAZAC code of differentsequences and/or different block spread codes. These are specified bythe code information and resource information unit 742.

As mentioned above, since the whole CAZAC code is merely multiplied byone factor in each long block, the base station apparatus can add uplinkcontrol signals received from each user apparatus in phase. Therefore,when the block spread code is used, orthogonality of the code isexerted. In addition to that, orthogonality among CAZAC codes of thesame sequence having different cyclic shift amounts is not collapsed.Thus, the base station apparatus can orthogonally separates signals sentfrom each user apparatus. Even when non-orthogonal CAZAC code is used,the user apparatus can be identified with lower interference as comparedwith the case in which a random sequence is used. Further, bydetermining the contents of the first to twelfth factors used for theuplink control signal for each user apparatus, contents ofacknowledgement information and/or channel state information can beidentified.

In step B3, the base station apparatus performs processing such asretransmission control and resource assignment based on acknowledgementinformation (ACK/NACK) and/or channel state information (CQI) reportedfrom the user apparatus by the uplink control signal.

According to the present embodiment, the mapping position of theinformation addressed to the user apparatus in the downlink L1/L2control signal and resources for the uplink control signal includingACK/NACK are uniquely determined by using the predeterminedcorrespondence relationship. Thus, it becomes unnecessary to reportresources to be used for the uplink control signal one by one. Since itis only necessary to prepare resources for (the number of multiplexedusers and the number of times of retransmission) at most, resources canbe saved as compared with the after-mentioned second embodiment.

Embodiment 2

FIG. 13 shows a block diagram of the user apparatus according to asecond embodiment of the present invention. In general, the userapparatus is similar to one described with reference to FIG. 2. But, theuser apparatus shown in FIG. 13 is different from one shown in FIG. 2 inprocessing of the unit 340′ for determining resource block number of thedownlink data signal, and the code information and resource informationunit 342′.

The unit 340′ for determining the resource block number of the downlinkdata signal extracts control information addressed to the user apparatusfrom the downlink L1/L2 control signal, and determines a resource blockto which the downlink data signal addressed to the user apparatus ismapped. For the sake of explanation, it is assumed that the downlinkdata signal is transmitted to the user apparatus using a Y-th resourceblock (RB-Y).

In addition to specifying code information like the unit 342 shown inFIG. 2, the code information and resource information unit 342′ refersto a list indicating correspondence relationship between the location(RB-Y) of the resource block used for the downlink data signal andresources of the uplink control signal, and specifies which resourceshould be used for transmitting the uplink control signal including theacknowledgement information. The specified code information andresources are reported to each component like the case of the firstembodiment.

FIG. 14 shows a block diagram of the base station apparatus according tothe second embodiment of the present invention. In general, the basestation apparatus shown in FIG. 14 is similar to one shown in FIG. 7.But, the base station apparatus shown in FIG. 14 is different from thatshown in FIG. 7 in processing on the code information and resourceinformation unit 742′. First, the scheduler 722 reports informationindicating a resource block to which the downlink data signal addressedto each user apparatus is mapped, to the code information and resourceinformation unit 742′. Assuming that a data signal addressed to a userapparatus is mapped to a Y-th resource block (RB-Y), informationindicating that “the resource block is RB-Y” is reported to the codeinformation and resource information unit 742′ as to the user apparatus.

In addition to specifying code information like 742 shown in FIG. 7, thecode information and resource information unit 742′ refers topredetermined correspondence relationship between the resource blocknumber (RB-Y) and resources of the uplink control signal includingACK/NACK for the data signal transmitted using the resource block, sothat the code information and resource information unit 742′ specifieswhich resource should be used for transmitting the uplink control signalin the future.

FIG. 15 shows an example of the correspondence relationship. In theexample shown in the figure, as to 16 resource block numbers, ACK/NACKfor the first to eighth resource blocks are transmitted by the firsthopping control signal (FIG. 1), and ACK/NACK for the ninth to sixteenthresource blocks are transmitted by the second hopping control signal(FIG. 1).

In the present embodiment, since the resource block number used for theuser apparatus and the resources for the uplink control signal includingACK/NACK are uniquely determined by the predetermined correspondencerelationship, it is not necessary to report, to the user apparatus,information indicating which resource should be used for uplink controlsignal one by one. Since resources for the uplink control signal areuniquely derived from the resource block number used for the userapparatus, it is not necessary to identify whether the data signaltransmitted by the resource block is based on persistent scheduling ornot. In addition, since the resource block number is used as a basis,instead of using the mapping position of the control signal like thefirst embodiment, resources for uplink control signal can be easilyspecified.

As described above, while the present invention is described withreference to specific embodiments, the respective embodiments are merelyexemplary, so that a skilled person will understand variations,modifications, alternatives, and replacements. While specific numericalvalue examples are used to facilitate understanding of the presentinvention, such numerical values are merely examples, so that anyappropriate value may be used unless specified otherwise. Classificationinto each embodiment is not essential in the present invention, andequal to or more than two embodiments may be used as necessary. Forconvenience of explanation, while the apparatus according to theembodiments of the present invention is explained using functional blockdiagrams, such an apparatus as described above may be implemented inhardware, software, or a combination thereof. The present invention isnot limited to the above embodiments, so that variations, modifications,alternatives, and replacements are included in the present inventionwithout departing from the spirit of the present invention.

The present international application claims priority based on Japanesepatent application No. 2007-073724, filed in the JPO on Mar. 20, 2007and the entire contents of the Japanese patent application No.2007-073724 is incorporated herein by reference.

1. A user apparatus for transmitting an uplink control signal to a basestation apparatus using a single carrier scheme, comprising: a receivingunit configured to receive a downlink control signal and a downlink datasignal; a determination unit configured to prepare acknowledgementinformation indicating positive acknowledgement or negativeacknowledgement for the downlink data signal; a code information andresource information unit, in which a correspondence relationship thatuniquely associates a resource of the downlink control signal with aresource to be used for the uplink control signal is defined, configuredto specify a resource to be used for the uplink control signal based ona resource of the downlink control signal received by the receiving unitaccording to the correspondence relationship; and a transmission unitconfigured to generate the uplink control signal including theacknowledgement information and transmit the uplink control signal basedon the resource specified by the code information and resourceinformation unit.
 2. The user apparatus as claimed in claim 1, whereinthe code information and resource information unit specifies a cyclicshift amount and a frequency band as the resource to be used for theuplink control signal, and the transmission unit generates the uplinkcontrol signal by multiplying an orthogonal code sequence by theacknowledgement information prepared in the determination unit, theorthogonal code sequence being cyclically rearranged with the cyclicshift amount specified by the code information and resource informationunit, and the transmission unit transmits the uplink control signalusing the frequency band specified by the code information and resourceinformation unit.
 3. The user apparatus as claimed in claim 2, whereinthe code information and resource information unit specifies a blockspread code, and the transmission unit generates the uplink controlsignal also using the block spread code specified by the codeinformation and resource information unit.
 4. The user apparatus asclaimed in claim 1, wherein the correspondence relationship uniquelyassociates an OFDM symbol to which the downlink control signal for theuser apparatus is mapped with a time slot to which the uplink controlsignal is mapped.
 5. The user apparatus as claimed in claim 1, wherein,when communication is performed by persistent scheduling in downlink,the uplink control signal including the acknowledgement information istransmitted using a resource different from a resource for a userapparatus that is not performing persistent scheduling.
 6. The userapparatus as claimed in claim 1, wherein the uplink control signalincludes a plurality of unit block sequences each of which is obtainedby multiplying all chips of an orthogonal code sequence for the userapparatus by a same factor.
 7. The user apparatus as claimed in claim 6,wherein factors by which each of a plurality of unit blocks having thesame contents is multiplied represent an orthogonal code sequence.
 8. Acommunication method for use in a mobile communication system which usesa single carrier scheme in uplink, comprising the steps of: receiving adownlink control signal and a downlink data signal; preparingacknowledgement information indicating positive acknowledgement ornegative acknowledgement for the downlink data signal; specifying aresource to be used for the uplink control signal based on a resource ofthe downlink control signal received in the receiving step, according toa correspondence relationship that uniquely associates a resource of thedownlink control signal with a resource to be used for the uplinkcontrol signal; and generating the uplink control signal including theacknowledgement information and transmitting the uplink control signalbased on the specified resource.
 9. A communication system comprising: auser apparatus for transmitting an uplink control signal using a singlecarrier scheme; and a base station apparatus for receiving the uplinkcontrol signal from the user apparatus, the user apparatus comprising: areceiving unit configured to receive a downlink control signal and adownlink data signal from the base station apparatus; a determinationunit configured to prepare acknowledgement information indicatingpositive acknowledgement or negative acknowledgement for the downlinkdata signal; a code information and resource information unit, in whicha correspondence relationship that uniquely associates a resource of thedownlink control signal with a resource to be used for the uplinkcontrol signal is defined, configured to specify a resource to be usedfor the uplink control signal based on a resource of the downlinkcontrol signal received by the receiving unit according to thecorrespondence relationship; and a transmission unit configured togenerate the uplink control signal including the acknowledgementinformation and transmit the uplink control signal based on the resourcespecified by the code information and resource information unit.